1. Field of the Invention
The present invention relates to a lens system for electrically driving a movable optical member in response to a drive command from a commanding apparatus, and more particularly, to a broadcasting television lens system.
2. Description of the Related Art
Heretofore, a television lens used for television broadcast is detachably attachable to a television camera. The television lens includes multiple movable optical members for variable adjustments of zooming and focusing as like. The movable optical members may be electrically driven in response to commands from a commanding apparatus. There are exemplified, as the commanding apparatus, a zoom demand for variable adjustment of zooming and a focus demand for variable adjustment of focusing. The television lens is usually connected to the zoom demand and the focus demand through cables. A structure of the conventional television lens described above is illustrated in FIG. 6 included in Japanese Patent Application Laid-Open No. H08-334673.
Further, Japanese Patent Application Laid-Open No. 2007-293070 proposes a lens system in which the television lens is wirelessly connected to the zoom demand and the focus demand, to thereby enhance ease of operation and maintenance, and to improve reliability.
When a wireless communication function described in Japanese Patent Application Laid-Open No. 2007-293070 is provided to establish wireless connection between the lens apparatus and the commanding apparatus, a battery is used as a power supply on the commanding apparatus side. Japanese Patent Application Laid-Open No. 2007-293070 describes that a wireless LAN, Bluetooth system, or a Zigbee system are used as a wireless communication system.
Each of the wireless communication systems is a master/slave communication system. That is, periodic polling from an apparatus side set as a master to an apparatus side set as a slave is performed. Data communication from the master to the slave is performed after activation of the polling. Communication from the slave side to the master side is performed in response to the polling. However, Japanese Patent Application Laid-Open No. 2007-293070 does not describe a method of determining which communication apparatus is set as the master or the slave.
Japanese Patent Application Laid-Open No. 2002-280925 discloses a master-slave setting method for a wireless communication apparatus.
In Japanese Patent Application Laid-Open No. 2002-280925, when the wireless communication apparatus is supplied with power from an AC adapter, the wireless communication apparatus is set as the master. When the wireless communication apparatus is supplied with power from a battery, the wireless communication apparatus is set as the slave, to thereby reduce electric consumption when battery-operated.
Consideration is given to a case where a master/slave setting is made for a wireless communication function as in Japanese Patent Application Laid-Open No. 2002-280925 in the structure described in Japanese Patent Application Laid-Open No. 2007-293070. The commanding apparatus side is battery-operated, and hence the wireless communication function of the commanding apparatus side is set as the slave function.
When the wireless communication function of the commanding apparatus side is set as the slave function, low electric consumption is achieved, and hence the availability of the battery is improved. However, a command signal is sent after polling from the master side which is the lens apparatus, which leads to a problem that responsiveness is deteriorated.
The commanding apparatus is categorized into two types, namely, an analog demand for sending an analog signal as a command value to the lens apparatus and a digital demand for sending the command value to the lens apparatus through digital communication. When the lens apparatus and the commanding apparatus are wirelessly connected to each other by the wireless communication function, the amount of data sent from the commanding apparatus to the lens apparatus varies between the analog demand and the digital demand. In general, the amount of data in the digital demand is several times larger than the amount of data in the analog demand. Therefore, when the lens apparatus and the commanding apparatus are wirelessly connected to each other by the wireless communication function, there arises a problem that the responsiveness in the digital demand is further deteriorated as compared with the responsiveness in the analog demand.